Sound

Question 0

What is compression

Answer 0

When particles are pushed against neighbouring particles

Question 1

How do we hear sound

Answer 1

Produced by vibrating objects and we hear the sound when these vibrations which travel as sound waves reach our ears
The strike the ear drum making it vibrate and these vibrations are turned into electrical signals detected by the brain

Question 2

What is rare fraction

Answer 2

Area behind the compression where the particles spread out

Question 3

What is a longitudinal sound wave

Answer 3

Wave created after the cone of compressions and rarefactions has vibrated several times

Question 4

What can sound waves travel through

Answer 4

Solid
Liquids
Gases
Not vacuums because no particles to carry the vibrations

Question 5

What is the sound of speed

Answer 5

Air 340m/s 
Seawater 1500m/s
Concrete 5000m/s
Varies with temperature and pressure
Sounds travels faster through solids

Question 6

How to measure echoes

Answer 6

Stand a distance away from a friend and they will clap to piece of wood together
Watch it, start the stopwatch, and stop it when you hear the sound
This will be inaccurate due to reaction time

Question 7

How to measure the speed of sound

Answer 7

Sound of echoes
Use resonance tube an tuning fork
Use an oscilloscope

Question 9

How to use resonance tube and tuning fork

Answer 9

Standing wave created when air vibrates in a tube- sound wave is reflected
Gives wave larger amplitude
Water adjusted in resonance tube to change height
Sound (with a known frequency) is created by striking a tuning fork and holding it above the tube
Water height is adjusted until the loudest sound is heard

Question 10

Rope analogy of sound waves

Answer 10

Spin end of a rope with other side connected to the wall
This sets up a standing wave
Wave sent down rope by hand is reflected so makes standing wave
use the formula to obtain the speed of sound

Question 11

Principle of resonance tube and tuning fork

Answer 11

The first resonance will be heard when the length of air in the tube is equal to a quarter of the wavelength
The next is when the air is equal to three quarters of the wavelength

Question 12

How to measure the speed of sound using an oscilloscope

Answer 12

Attach two microphones to an oscilloscope
Set the microphones next to each other at a small distance
Connect a loudspeaker to a single generator and set down close to the microphones
Set the generator to produce sound with a frequency of 1kHz
Move one microphone further away from the loudspeaker gradually
Observe the oscilloscope and when the two sound waves are exactly parallel, this is when the microphones are 1 wavelength away from each other
Measure this distance to get the wavelength
Use oscilloscope screen to get the frequency
Use the formula to get speed of sound

Question 13

Rule of reflection

Answer 13

Sound waves are reflected from a surface so tat the angle of incidence is equal to the angle of reflection

Question 14

Uses of reflection

Answer 14

(SONAR)- ships can emit a sound toward the sea bed and when the echo is detected the depth of the sea can be calculated

Question 15

Diffraction of sound waves

Answer 15

Some sound waves have a wavelength of a door frame
These sound wave would spread out as they pass through the door
If they were not diffracted sound could not travel through the doorframe and these are ‘sound shadows’

Question 16

Pitch rule

Answer 16

Small objects, faster vibrations, higher frequency, higher pitch
Large objects, slower vibrations, lower frequency, lower pitch

Question 17

What is frequency

Answer 17

Measured in hertz (Hz) and is the number of complete vibrations made by a source

Question 18

Using a CRO

Answer 18

CRO= cathode ray oscilloscope
Low pitched sounds would show less complete waves on the screen as it has less complete waves per second
High pitched sounds would show many complete waves per second

Question 19

Humans audible sound range

Answer 19

20Hz - 20, 000Hz
Varies from person to person
Younger people can hear higher frequencies than adults

Question 20

What is ultrasound

Answer 20

Objects which vibrate at higher frequencies then the human audible range includes eg dolphins

Question 21

Opposite of ultrasound

Answer 21

Infrasounds are objects which vibrate at lower frequencies then the human audible range includes eg elephants

Question 22

Volume

Answer 22

Drum struck harder, more energy transferred, drum skin moves up and down with large amplitude=regions of compressed air molecules which carry lots of energy and we hear a loud sound
Drum struck gently, less energy transferred, small amplitude, less dense compressions, less energy transferred, we hear quieter sound